1. Field of the Invention
This invention relates to well pipe packers and more specifically to apparatus for retarding the extruding action of resilient material in such packers, which action in the prior art structure resulted in shortened packer life and occasional packer failure.
2. Description of the Prior Art
The walls of well pipe or casing are plugged or packed off, from time to time, for a number of reasons. For example, a section of well pipe may be packed off to permit pressuring the section to detect leaks in the wall of the well pipe. The structure used to seal off the walls of a well pipe is known as a packer and generally comprises an expandable portion that is activated from a non-expanded size, permitting it to freely pass through the bore hole of the well pipe, to a radially enlarged size that accomplishes the desired sealing engagement.
Such packer structures in the prior art comprise a variety of component parts. Generally, however, the packer parts include a combination of metallic and resilient components. One common type includes an expandable segment metallic ring surrounded by a resilient packer sleeve. Another common type includes telescoping metallic parts that squeeze together to cause an intermediate resilient packer element to expand radially.
Many of these structures include top and bottom facing elements one or both of which include sloping or irregular contours. These surfaces assist in achieving effective sealing between components. An example of a structure including components with contoured facings is shown in U.S. Pat. No. 3,195,645, disclosing annular ring elements 28 and 30 with cone-shaped faces.
Such contoured surfaces generally permit a slight longitudinal movement of the expandable component as it radially expands and such structure involves two mating surfaces that are similarly contoured.
Although such a structure permits a uniform and even contact between the mating parts, components at least partially made of resilient or conformable material, operating under the high pressure conditions to which they are often subjected, are not protected by such a design. In fact, such a design in many cases accelerates the wear on such components and even on occasion promotes malfunctioning.
Such wear and malfunction results from the expansion of the resilient component in operation. Once the resilient material has expanded to contact the well pipe, further expansion is restricted by the well pipe and by the upper and lower mating surfaces. Under further compression, the resilient material will tend to extrude vertically along the well pipe wall, thereby degrading the structural integrity of the material.
It is therefore a feature of this invention to provide an improved well pipe packer assembly which minimizes the extrusion of resilient components therein when the packer is expanded in place.
It is another feature of this invention to provide an improved well pipe packer assembly which causes resilient components therein to expand radially without overlapping the non-resilient components between the packer and the wall of the well pipe or between segmented parts of expanded non-resilient components.
It is still another feature of the invention to provide an improved well pipe packer assembly including a washer that does not deform under operating pressure nor break or chip under such pressure.
It is still another feature of the invention to provide an improved well pipe packer assembly including a washer having one sloping surface to prevent an adjacent resilient packer component from undergoing peripheral extrusion and having a second sloping surface for expanding a segmented packer ring, thereby retarding vertical extrusion of the resilient packer component under high pressure conditions.